Separation of galactic and extragalactic radio emission at decameter wavelengths

Vasilenko, N. M.; Sidorchuk, M. A.

doi:10.1007/s10509-017-3202-0

Cited by 4 publications

(1 citation statement)

References 44 publications

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“…The best fit to the data in this case has a background temperature of 26.6±2.5 K at 310 MHz and a spectral index of -2.44±0.05. This shallower slope is consistent with the results of Fornengo et al (2014) and Vasilenko & Sidorchuk (2017) but does not dramatically alter the temperature at 1.4 GHz of 0.654 +0.113 −0.102 K. Furthermore, we note that this still requires a separate source of radiation in addition to the expected background from known source counts.…”

Section: Resultssupporting

confidence: 90%

The Radio Background below 100 MHz

Dowell

Taylor

2018

ApJL

123

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The recent detection of the "cosmic dawn" redshifted 21 cm signal at 78 MHz by the EDGES experiment differs significantly from theoretical predictions. In particular, the absorption trough is roughly a factor of two stronger than the most optimistic theoretical models. The early interpretations of the origin of this discrepancy fall into two categories. The first is that there is increased cooling of the gas due to interactions with dark matter, while the second is that the background radiation field includes a contribution from a component in addition to the cosmic microwave background. In this paper we examine the feasibility of the second idea using new data from the first station of the Long Wavelength Array. The data span 40 to 80 MHz and provide important constraints on the present-day background in a frequency range where there are few surveys with absolute temperature calibration suitable for measuring the strength of the radio monopole. We find support for a strong, diffuse radio background that was suggested by the ARCARDE 2 results in the 3 to 10 GHz range. We find that this background is well modeled by a power law with a spectral index of -2.58±0.05 and a temperature at the rest frame 21 cm frequency of 603 +102 −92 mK.

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Section: Resultssupporting

confidence: 90%

The Radio Background below 100 MHz

Dowell

Taylor

2018

ApJL

123

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The Founder of the Decameter Radio Astronomy in Ukraine Academician of Nas of Ukraine Semen Yakovych Braude Is 110 Years Old: History of Creation and Development of the National Experimental Base for the Last Half Century

Konovalenko¹,

Захаренко²,

Lytvynenko³

et al. 2021

Radio phys. radio astron.

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Purpose: A historical review of the experimental baselopment of low-frequency radio astronomy in Ukraine, its foundation half a century ago by an outstanding scientist S.Ya. Braude to the current state. Design/methodology/approach: The constant progress of electronic, computer and digital technologies, information and telecommunication technologies, theory and practice of antenna and receiving systems design, which introduction enriched the hardware and methodological ideology of construction and usage of the UTR-2, URAN, and GURT radio telescopes, have been used. Findings: The worldwide most effective national experimental radio astronomy means, the UTR-2, URAN, and GURT decameter-meter wave radiotelescopes, have been created and improved. The best combination of the systems main parameters: sensitivity; frequency band; spatial, frequency and temporal resolutions; noise immunity; uniformity of amplitude-frequency and space-frequency characteristics and multifunctionality has been provided. Conclusions: For the half a century of radio astronomical scientific and technical at the Institute of Radio Astronomy of NAS of Ukraine, the high astrophysical informativeness of the low-frequency radio astronomy and the possibility of creating a highly efficient experimental base – giant radio telescopes of decameter-meter wavebands have been proved. Today, the Ukrainian radio telescopes are well known and recognized world-wide being indispensable and most in demand by the scientific community. The founder of the decameter radio astronomy in Ukraine, the eminent scientist Semen Yakovych Braude was not mistaken when he decided to start radio astronomical explorations. The memory of him will always remain in the minds and hearts of many generations. Key words: low-frequency radio astronomy; radio telescope; phase shifter; antenna amplifier; digital signal recorder; effective area; sensitivity; resolution; noise immunity

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50 Years of Research in Continuum at the Utr-2 Radio Telescope

Sidorchuk

Vasilenko

Ulyanov

et al. 2021

Radio phys. radio astron.

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Purpose: The results of research in continuum decameter-wave radio emission of the Galaxy background, ionized hydrogen regions, supernova remnants, extragalactic discrete sources, extended galaxies, galactic clusters, extragalactic background are given. The aim of this work is reviewing the results achieved for over 50-years of the UTR-2 radiotelescope research of our Galaxy and its population, as well as extragalactic radio sources in the continuum radio emission spectrum at extremely low frequencies for the ground based observations. Design/methodology/approach: The review, analysis, collection of archival data in various publications related to the subjectof this work. Findings: The basic results of studying the ionized hydrogen regions, supernova remnants, Galaxy background emission and its large-scale structure are given, and the maps of these sources are obtained. The catalog of extragalactic discrete radio sources of the most Northern sky part and the cosmological conclusions based on its analysis are described; the estimate of the isotropic extragalactic background brightness temperature is obtained; for the first time, the observational results for the Andromeda galaxy and two galactic clusters Coma and A2255 are given briefly. Conclusions: All the results presented here emphasize the uniqueness and importance of research in the decameter wavelength range, and the large area, flexibility of structure, continuous improvement make the UTR-2 radio telescope an indispensable tool for solving the most important tasks of modern radio astronomy, despite its respectable age. For example, only in the range of 10 to 30 MHz the ionized part of the most common element in the universe, the hydrogen, becomes optically thick and begins to absorb the synchrotron emission on the line of sight, which allows rather easy separation of thermal and non-thermal components of radioemission. This property allows to determine the ionized hydrogen regions’ electron temperature and the electron concentration on the line of sight independently in studying the hydrogen emission regions. When studying the supernova remnants, we can determine the ionized matter location by their spectrum drops ‒ before, inside or behind the remnant. Based on the HB3 supernova remnant radio imagies, an assumption was made on the existence of an ionized hydrogen relic shell aroundit, being caused by the initial ultraviolet flash of a supernova. For the first time, the maps of the Northern sky large-scale structure in the declination range from ‒15° to +85° at extremely low frequencies 10, 12.6, 14.7, 16.7, 20 and 25 MHz for the ground-based observations are published, which, besides their own scientific value, may allow to correct the UTR-2 radio telescope imaging results. Using the full-resolution UTR-2 maps and the developed method of multifrequency T‒T diagrams, it was possible to separate the background radiation into galactic and extragalactic components and construct the spectrum of the latter. From the analysis of the most complete decameter wavelength range catalog of discrete sources, it follows that there is a gap in the redshift spatial distribution for all classes of extragalactic sources. The existence of an ionized hydrogen ring in the Andromeda Nebula disk has been suggested. It is shown that the main partof the galaxy clusters decameter-wave emission comes from haloes and relics. Key words: decameter range; discrete sources; supernovaremnants; catalog; continuum radio emission; HII regions; UTR-2; background emission

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Separation of galactic and extragalactic radio emission at decameter wavelengths

Cited by 4 publications

References 44 publications

The Radio Background below 100 MHz

The Radio Background below 100 MHz

The Founder of the Decameter Radio Astronomy in Ukraine Academician of Nas of Ukraine Semen Yakovych Braude Is 110 Years Old: History of Creation and Development of the National Experimental Base for the Last Half Century

50 Years of Research in Continuum at the Utr-2 Radio Telescope

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